Reading Aquistar Smart Sensors with Campbell Loggers

Transcription

1 Introduction Instrumentation Northwest now offers an easy-to-read Modbus version for several of their popular AquiStar Smart Sensors. These sensors communicate via Modbus RTU and directly return measurement readings, without any further math on the part of the host system. Currently, this feature is available on the PT2X Pressure/Temperature Sensor, the CT2X Conductivity/Temperature/Pressure Sensor, the T32 1Wire Temperature Logger, the GDL Datalogger, and the TempHion ph/ise/redox sensor. The purpose of this document is to provide information on how to read INW s AquiStar Smart Sensors with a Campbell datalogger via Modbus. Refer also to Modbus Direct Read on AquiStar Smart Sensors (Document # 9C0225) for information on available measurement units on the various sensors. Wiring On a CR1000, sensors can be connected using either the Com1, Com2, Com3, or Com4 ports or the RS232 port. Some loggers do not have an RS232 port. On these loggers, you will have to use the Com1, Com2, etc. ports. Using the Com1, Com2, Com3, or Com4 Port ENGINEERING DEPARTMENT Page 1 of 10

2 Using the RS232 Port on a CR1000 Taking Measurements Modbus Function Measurements can be read using Modbus function 03 Read Holding Registers. Data Format The data is returned as a 32-bit IEEE floating-point value, high word first, also referred to as big-endian or float inverse. Reading Registers You can read single values by reading the register set for the desired value. For example, to read only conductivity in a linear format from a CT2X, you would read two registers starting at You can also read any contiguous sets of registers by starting at the register for the first value you want to read and specifying how many registers to read (two per channel). For example, to read all channels on a standard GDL, you would read 14 registers starting at ENGINEERING DEPARTMENT Page 2 of 10

3 Register Addresses for PT2X, CT2X, TempHion, and T32 Sensor Type PT2X PT2X CT2X TempHion T32 Firmware 1.5 >= 2.1 >= 1.5 >= 1.1 any Register Address Pressure Temperature Temperature Temperature Temperature Temperature Pressure Conductivity - Linear mv-1 (in mv) Temperature Conductivity - non-linear mv-2 (in mv) Temperature Pressure mv-3 (in mv) Temperature mv-1 (in ph, ppm, or Eh) Temperature mv-2 (in ph, ppm, or Eh) Temperature mv-3 (in ph, ppm, or Eh) Temperature Temperature Temperature Temperature Temperature Temperature Temperature Temperature Temperature Temperature Temperature Temperature Temperature Temperature Temperature Temperature Temperature Temperature Temperature Temperature Temperature Temperature Temperature Temperature Temperature Temperature - 32 ENGINEERING DEPARTMENT Page 3 of 10

4 Register Addresses for GDL Sensor Type GDL GDL GDL GDL GDL Version Standard Dissolved Oxygen Heart Rate Monitor Rain Bucket Generic Digital Firmware >= 2.5 >= 2.5 >= 2.5 >= 2.5 >= 2.5 Register Address Temperature Temperature Temperature Temperature Temperature Temperature Temperature Temperature Temperature Temperature mv mv mv mv mv Voltage Voltage Voltage Voltage Voltage Voltage Voltage Voltage Voltage Voltage ma 4-20 ma 4-20 ma 4-20 ma 4-20 ma ma 4-20 ma 4-20 ma 4-20 ma 4-20 ma DO channel 1 Heart Rate Rainfall Custom Digital DO Temperature - 1 Custom Digital DO channel 2 Custom Digital DO Temperature - 2 Custom Digital DO channel 3 Custom Digital DO Temperature DO channel DO Temperature - 4 Sample Code The following pages contain sample code. The first sample reads a contiguous set of channels from a PT2X. To change this sample to work with your sensor, you will need to assign your sensor address, the starting register, number of channels to read, and the output column headers. The code is marked where you need to make the changes. The second sample reads two individual channels (linear conductivity and pressure) from a CT2X. To change this sample to work with your sensor, you will need to assign your sensor address, the starting registers, the final value array size, the number of output columns, the output column headers, and the number of reading sets. The code is marked where you need to make the changes In both samples there is a subroutine called DecodeIEEEFloat. This code should not be changed. It is called after the reading has been taken to convert the two register readings into one 32-bit IEEE Float format number. ENGINEERING DEPARTMENT Page 4 of 10

5 Direct Read Sample Code Range of Channels 'CR1000 Series Datalogger 'DirectRead_sample_range of channels.cr1 'Copyright Instrumentation Northwest, Inc 'This program reads an INW Smart Sensor beginning with the first channel 'and reading two channels in a row 'This particular version reads a PT2X with firmware 2.1 or higher 'Temperature channel first and then the Pressure channel. '*************** Constants and Variables ********************************************* Const SNSR_ADDR = 3 ' Assign sensor address here!!! Const TAKE_MEASUREMENT = ' Modbus address to begin readings Const NUM_CHANNELS = 2 ' Number of channels to read Const NUM_REGISTERS = NUM_CHANNELS*2 Public Result Public sensor(num_registers) As Long ' Array to hold values read Public values(num_channels) ' Array to hold final values Assign your sensor address, the starting register, and number of channels to read here. Public temperature As Float Public pressure As Float ' Temperature ' Pressure '*************** Define DataTables here, as desired ************************************ DataTable(Readings,True,-1) Sample(1,values(1),IEEE4) FieldNames("Temperature") Sample(1,values(2),IEEE4) FieldNames("Pressure") EndTable 'Column header for 1st channel 'Column header for 2nd channel Assign output column headers here. '************************* Subroutine DecodeIEEEFloat ************************************* ' This subroutine takes two 16-bit registers and decodes them into ' a single IEEE 32-bit floating point value. ' This subroutine is called after taking Modbus readings to decode the data. ' You should not modify this subroutine, just use as is. Sub DecodeIEEEFloat (HW, LW, r) '************************************************************************************** 'Take 32-bit value comprising two words, high word first, 'and convert to IEEE bit floating point 'Bit 31: sign bit 'Bits 30-23: exponent 'Bits 22-0: mantisssa ENGINEERING DEPARTMENT Page 5 of 10

6 Dim man Dim ex Dim sign Dim a Dim b Dim c 'mantissa 'exponent 'sign 'interim value 'interim value 'interim value 'special case If HW = 0 AND LW = 0 Then r = 0 Exit Sub End If 'Pull the 23 bit mantissa from the two separate words man = LW + ((HW And ((2 ^ 7) - 1)) * 2 ^ 16) 'Get exponent a = 2 ^ 7 b = (2 ^ 8) - 1 ex = (Int(HW / a)) And b 'Get sign 'sign = Int(HW / (2 ^ 16)) And (2 ^ 1-1) If HW < 0 Then sign = 1 Else sign = 0 End If 'Compute final value c = 1 + man / (2 ^ 23) r = ((-1) ^ sign) * c * (2 ^ (ex - 127)) End Sub '*********************** Begin Program ************************************************* BeginProg Dim i '*************************************************************************************** '**************** Scan Loop ************************************************** ENGINEERING DEPARTMENT Page 6 of 10

7 Scan (5,Sec,0,0) 'ModBusMaster ( ResultCode, ComPort, BaudRate, ModBusAddr, Function, Variable, ' Start, Length, Tries, TimeOut ) 'wake up the sensor and wait 1 second for it to warm up ModBusMaster (Result,ComRS232,38400,SNSR_ADDR,3,sensor(),TAKE_MEASUREMENT,NUM_REGISTERS,3,100) Delay (0,1,sec) 'take a measurement ModBusMaster (Result,ComRS232,38400,SNSR_ADDR,3,sensor(),TAKE_MEASUREMENT,NUM_REGISTERS,3,100) ' extract values, convert each set of two registers into one floating point value and put in values array For i = 1 To NUM_REGISTERS step 2 DecodeIEEEFloat (sensor(i), sensor(i+1), values((i+1)/2)) Next i CallTable Readings NextScan EndProg Direct Read Sample Results Range of Channels TIMESTAMP RECORD Temperature Pressure 9/23/ : /23/ : /23/ : Direct Read Sample Code Individual Channels 'CR1000 Series Datalogger 'DirectRead_sample_individual channels.cr1 'Copyright Instrumentation Northwest, Inc 'This program reads two individual channels from an INW Smart Sensor 'This particular version reads the Linear Conductivity value and the Pressure ' from a CT2X with firmware 1.5 or higher '*************** Constants and Variables ********************************************* Const SNSR_ADDR = 1 ' Assign sensor address here!!! Const TAKE_MEASUREMENT1 = ' Modbus address for first reading '(in this case conductivity (linear) Const TAKE_MEASUREMENT2 = ' Modbus address for second reading '(in this case pressure) Assign your sensor address and the starting register for each channel you want to read. ENGINEERING DEPARTMENT Page 7 of 10

8 'Add further Consts as are needed for the number of individual channels you want to read. Public Result Public reading(2) As Long ' Array to hold values read each time a channel is read Public values(2) As Float ' Array to hold final values, one value per channel '*************** Define DataTables here, as desired ************************************ DataTable(Readings,True,-1) Sample(1,values(1),IEEE4) FieldNames("Conductivity") Sample(1,values(2),IEEE4) FieldNames("Pressure") EndTable 'Column header for 1st channel 'Column header for 2nd channel '************************* Subroutine DecodeIEEEFloat ************************************* ' This subroutine takes two 16-bit registers and decodes them into ' a single IEEE 32-bit floating point value. ' This subroutine is called after taking Modbus readings to decode the data. ' You should not modify this subroutine, just use as is. Sub DecodeIEEEFloat (HW, LW, r) '************************************************************************************** 'Take 32-bit value comprising two words, high word first, 'and convert to IEEE bit floating point 'Bit 31: sign bit 'Bits 30-23: exponent 'Bits 22-0: mantisssa Dim man 'mantissa Dim ex 'exponent Dim sign 'sign Dim a 'interim value Dim b 'interim value Dim c 'interim value 'special case If HW = 0 AND LW = 0 Then r = 0 Exit Sub End If Make the size of this array equal to the number of channels you want to read. Assign output column headers here, adding Sample statements for each channel you want to read 'Pull the 23 bit mantissa from the two separate words man = LW + ((HW And ((2 ^ 7) - 1)) * 2 ^ 16) 'Get exponent a = 2 ^ 7 b = (2 ^ 8) - 1 ex = (Int(HW / a)) And b ENGINEERING DEPARTMENT Page 8 of 10

9 'Get sign 'sign = Int(HW / (2 ^ 16)) And (2 ^ 1-1) If HW < 0 Then sign = 1 Else sign = 0 End If 'Compute final value c = 1 + man / (2 ^ 23) r = ((-1) ^ sign) * c * (2 ^ (ex - 127)) End Sub '*********************** Begin Program ************************************************* BeginProg Dim i '*************************************************************************************** '**************** Scan Loop ************************************************** Scan (5,Sec,0,0) 'ModBusMaster ( ResultCode, ComPort, BaudRate, ModBusAddr, Function, Variable, ' Start, Length, Tries, TimeOut ) 'wake up the sensor and wait 1 second for it to warm up ModBusMaster (Result,ComRS232,38400,SNSR_ADDR,3,reading(),TAKE_MEASUREMENT1,2,3,100) Delay (0,1,sec) 'Read first channel ModBusMaster (Result,ComRS232,38400,SNSR_ADDR,3,reading(),TAKE_MEASUREMENT1,2,3,100) ' extract values, convert set of two registers into one floating point value and put in values array DecodeIEEEFloat (reading(1), reading(2)), values(1)) 'Read second channel ModBusMaster (Result,ComRS232,38400,SNSR_ADDR,3,reading(),TAKE_MEASUREMENT2,2,3,100) ' extract values, convert set of two registers into one floating point value and put in values array DecodeIEEEFloat (reading(1), reading(2)), values(2)) EndProg 'Repeat for additional channels as needed CallTable Readings NextScan Repeat the channel reading code for each channel you want to read, changing the register address and values array location, as needed. ENGINEERING DEPARTMENT Page 9 of 10

10 Direct Read Sample Results Individual Channels TIMESTAMP RECORD Conductivity Pressure 9/23/ : /23/ : /23/ : /23/ : AquiStar is a registered trademark of Instrumentation Northwest, Inc. Modbus is a registered trademark of Schneider Electric. ENGINEERING DEPARTMENT Page 10 of 10